Electron tube structure



Uitc States Patent @fiice 2,693,545 Patented Nov. 2, 1954 ,59 5. LE TRQN UBE RUCTURE. William W. Eitel, Woodside, Jack.A, McCullough, Millbrae, Harold E. Sorg, Redwood. City, and Clayton E. Murdock, Millbrae, C'aiifi, assignors topEitel-McCul- Rough, Inc., San Bruno, Califi, a corporation of- California The present invention relates to atube structure adapted,

for use as a single tube in the conventional'manne'r or as a tube unit in a multi-unit, tube such as'disclosjed. in the.

patents of William W. Eitel and Jack A. McCullough, Nos. 2,424,683 and 2,424,685.

The broad object of our invention is to provide a tube structure having improved power capabilities in the higher frequency ranges.

Another object is to provide a tube structure of the character described having an improved filamentary cath ode capable of developingthe large quantities of electron emission required for pulse operation.

The invention possesses other objectsand features of advantage, some of which, with the foregoing, will be set forth in the following description of our.invention,' It is to be understood that we do notlimitourselve's to this disclosure of species of our invention, as we. may adopt variant embodiments thereof within the scope of the claims. 1

Referring to the drawing Figure l isa vertical sectional view of an electron tube Sirgcilll'e embodying the improvements of our invention; an

Figure 2 is a transverse sectional view taken in a plane indicated by line 2- 2 of Figure l.

In terms of broad inclusions, our electron tube structure comprises an envelope having 'a pair of coaxial cathode terminals adjacent one end'th'ereof, anda cathode in the envelope comprising a plurality of helical filaments, certain of the filaments being connected to one ofthe terminals and othersof the filaments being connected to the other terminal. An external anode is provided adjacent the other end ring is interposed in the envelope wall between the anode and the cathode terminals, The anode is preferably; of reentrant construction and a cooler for the anodeispreferably provided with acore projecting into thereentrant portion of the anode.

In greater detail and referring to the drawing, our tube structure comprises an evacuated envelope having an external anode 2 at the upper end and a cathode stem 3 at the lower end. The anode is of metal such as copper and is preferably of reentrant shape having a cup-shaped body 4 and an integral upturned flange 6 terminating in a downturned sealing ring 7. By this arrangement the sealing ring 7 is located well above the lower end of the main anode body 4, the reentrant portion of the anode forming an open annular cavity or space between body 4 and flange 6. A metal exhaust tubulation 8 on the anode body is pinched off at tip 9 after evacuation of the envelope.

A metallic grid terminal ring 11 is arranged below the anode and an envelope section 12 of vitreous material such as glass is sealed at its upper end to anode sealing ring 7 and at its lower end to grid terminal ring 11. Since glass section 12 extends upwardly to the upper end of anode flange 6 an ample glass path is provided between the anode and grid terminal ring for high voltage insulation purposes. Another glass envelope section 13, preferably of U-shape, is also sealed to the lower edge of the grid terminal ring for insulation purposes between the grid ring and cathode stem.

The cathode stem 3 comprises a pair of coaxial metallic terminals 14 and 16, the inner terminal 14 being preferably a solid prong and the outer terminal 16 of tubular shape surrounding the prong. A sealing flange 17 on the outer terminal 16 is sealed to the inner edge of envelope of the envelope, and a grid terminal 2 section13. The two cathode terminals are prong terminal 14 and a flange 21 on the outer tubular terminal 16. Flange 21 has a lower edge' registering with thatvof terminal 16, which edges are joined by a braze .22 made'a'fter the stem parts are assembled together.

' The cathode isof the filamentary type and comprises a plurality. of coaxial helical convolutions interposed between convolutions of adjacent filaments. These filaments are preferably of thoriated tungsten wire and after the filaments are mounted they are preferably carburized in' accordance with conventional practice. Any suitable number of filaments may be interspaced in this manner, four being shown in the tube illustrated. The upper ends of thefilaments are electrically and mechanically connected together by a circular cupshaped metal cap 24,to the rim of which the filaments are welded.

Supporting connections are provided for the lower ends of the filaments'so that one filament is connected to one, of the cathode terminals and an adjacent filament is connecte'd' tofthe other terminal. We preferably accomplish this by using a pair of flat circular supports 26 and 27 mounted one above the other on the cathode terminals. Upper support 26 is a disk secured to the top of center terminal 14 by screws 28, and lower support 27 is a ring welded in the end of tubular terminal 16. A pair of opposed pins 29 connected to and projecting upwardly from upper support 26 are welded to two of the filaments, andanother pair of pins 31 projecting from lower support 27 are welded to the other two filaments, suitable holes or openings 32 in the upper support being provided to .give clearance for pins 31.

Added support is preferably provided for the upper portion of the cathode structure by a center rod 33 secured to and projecting from the inner terminal 14. The tip end of the center rod extends through a center hole in cap 24 and an insulator 34 is interposed between the cap and center rod.

This multiple helix structure enables relatively large filamentary type cathodes to be built, using thoriated tungsten wire. The resulting structure is sufliciently rigid to tolerate close interelectrode spacings, and the multiplicity of individual helices provide a large total filament wire area, yet keeping the individual filament wires quite short. A cathode withsufiicient area to develop high orders of electron emission and at the same time having good mechanical strength is thus provided in conjunction with coaxial cathode terminals which are desirable from the standpoint of highfrequency circuits.

Control grid 36 is preferably of the cage type having longitudinal wire bars terminating at a base ring 37 and supported by a conical metal bracket 38 on a flange 39 secured to grid terminal ring 11. Both cathode and grid project into anode body 4, the grid being interposed between the cathode and anode in the usual manner. The grid terminal arrangement shown brings the grid connection out on the envelope wall at a point intermediate the anode and the cathode terminals, which is desirable from the circuit standpoint. It is also to be noted that the anode, grid terminal ring and cathode terminals are all coaxial with each other.

A cooler 41 is provided for dissipating heat from the anode. For cooling by forced air this cooler preferably comprises a core 42 of good heat conducting metal such as copper or aluminum having an annular lower portion projecting into the annular cavity formed by the reentrant portion of the anode. The upper portion of the core projects above the anode flange 6 and carries fins 43 which are radially extending strips of metal lying between retaining sleeves 44 and 46. A recess 47 is preferably provided in the upper portion of the core, about which the fins 43 are disposed, so as to reduce weight and provide a bet ter distribution of the metal in the core for conducting heat from the anode to the cooler fins 43. This recess also exposes more surface on the core for removing additional heat when a stream of air is directed downwardly against the cooler. If desired, fins may also be provided on the inner surface of the core within the recess 47, such as indicated by the dotted lines 48, in which case holes 49 connected by a. glass'r'ing 18 sealed betwfeena flange 19 on the inner.

filaments 23 each having are preferably provided to vent the recess. The tube envelope is exhausted prior to applying the cooler so that the anode may be brought up to a sufficiently high temperature during evacuation to insure complete outgassing of the anode metal. After exhaust the cooler core is soldered in place as by cadmium solder 51.

We claim:

1. An electron tube structure comprising an envelope having a pair of coaxial cathode terminals adjacent one end, and a cathode in the envelope comprising a plurality of helical filaments, the ends of certain of said filaments being connected to one of said terminals and the adjacent ends of others of the filaments being connected to the other terminal.

2. An electron tube structure comprising an envelope having a pair of coaxial cathode terminals adjacent one end, and a cathode in the envelope comprising a plurality of helical filaments connected together at their upper ends, the lower end of one of the filaments being connected to the inner of said terminals and the lower end of an adjacent filament being connected to the outer terminal, and means projecting from the inner terminal supporting the upper portion of the cathode.

3. An electron tube structure comprising an envelope having a pair of coaxial cathode terminals adjacent one end, a cathode in the envelope comprising a plurality of helical filaments, the lower end of one of the filaments being connected to the inner of said terminals and the lower end of an adjacent filament being connected to the outer terminal, a circular cap connecting the upper ends of the filaments, and a center rod projecting from the inher terminal supporting said cap.

4. An electron tube structure comprising an envelope having a pair of coaxial cathode terminals adjacent one end, a cathode in the envelope comprising a plurality of helical filaments, the lower end of one of the filaments being connected to the inner of said terminals and the lower end of an adjacent filament being connected to the outer terminal, a circular cap connecting the upper ends of the filaments, a center rod projecting from the inner terminal supporting said cap, and an insulator interposed between the cap and said center rod.

5. An electron tube structure comprising an envelope having a pair of coaxial cathode terminals adjacent one end, a pair of circular cathode supports disposed one above the other on said terminals, and a cathode in the envelope comprising a plurality of helical filaments, the ends of certain of said filaments being connected to one of said supports and the adjacent ends of others of the filaments being connected to the other support.

6. Anelectron tube structure comprising an envelope having a pair of coaxial cathode terminals adjacent one end, a pair of circular cathode supports disposed one above the other on said terminals, a plurality of rods projecting upwardly from the supports, said rods being posi- 4 tioned in a circle with adjacent rods projecting from different supports, and a cathode in the envelope comprising helical filaments connected to said rods.

7. An electron tube structure comprising a cathode having a plurality of coaxial helical filaments each with convolutions interposed between convolutions of adjacent filaments, a pair of supports for the lower end of the cathode, the lower ends of certain of the filaments being connected to one of said supports and the lower ends of others of the filaments being connected to the other support, and a third support supporting the upper end of the cathode, the upper ends of all of said filaments being connected to the third support.

8. An electron tube structure comprising a cathode having a plurality of coaxial helical filaments each with convolutions interposed between convolutions of adjacent filaments, a pair of supports for the lower end of the cathode, the lower ends of certain of the filaments being connected to one of said supports and the lower ends of others of the filaments being connected to the other support, a center rod, and a circular cap on the upper end of said rod, the upper ends of all of said filaments being connected to the rim of said cap.

9. An electron tube structure comprising a cathode having a plurality of coaxial helical filaments each with convolutions interposed between convolutions of adjacent filaments, a pair of supports for the lower end of the cathode, the lower ends of certain of the filaments being connected to one of said supports and the lower ends of others of the filaments being connected to the other support, a center rod, a circular cap on the upper end of said rod, the upper ends of all of said filaments being connected to the rim of said cap, and an insulator interposed between the cap and said rod.

10. An electron tube structure comprising a cathode having a plurality of coaxial helical filaments each with convolutions interposed between convolutions of adjacent filaments, a pair of circular cathode supports disposed below the cathode, a plurality of rods projecting upwardly from said supports, said rods being mounted in a circle with adjacent rods projecting from different supports, the lower ends of the filaments being connected to said rods, a center rod, and a circular cap on the upper end of the center rod, the upper ends of all of said filaments being connected to the rim of said cap.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,267,128 Mouromtseff et al Dec. 23, 1941 2,397,854 Glauber Apr. 2, 1946 2,422,465 Bondley June 17, 1947 2,431,337 Litton Nov. 25, 1947 

